1. Department of Mathematical Science, Faculty of Sciences, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia
2. UTM Centre for Industrial and Applied Mathematics, Institute Ibnu Sina for Scientific and Industrial Research, 81310 UTM Johor Bahru, Johor, Malaysia
3. Department of Mathematics, Faculty of Science, University of Kordofan, Elobied 51111, Sudan